1 or 2 new batteries?

That looks like the best solution for keeping a tight fit.

Two NOCO HM306BK boxes from Amazon are what I am using. They were the least expensive option I could find for GC2 batteries.

Originally posted by TheBum We have two Duracell brand GC2s on our 179. I can run my CPAP with the humidifier and not worry about running out of battery power. We also have an inverter to allow us to use charging adapters for our various devices as well as watch TV.

That is the brand I purchased and from the same source. I added a couple of USB charging outlets so that I don't need to use an inverter to charge our phones. We do have a 300 Watt inverter that we use for watching the TV. I should have gotten a smaller one except I once had a smaller one that didn't have enough power to run a laptop I used to own. That is why I got the 300 Watt one. The fan in it is a bit loud though, so I still may pick up a small one that has enough power to run the TV and keep the other one in case I need something with more power.

The onboard charger is more than enough to charge them back up. I have two 100 watt solar panels that in full sun can charge around 8.5 amps. Even when I had only one panel it was enough to recharge what I had used, as long as I had full sun on the panel

Originally posted by StephenH We do have a 300 Watt inverter that we use for watching the TV. I should have gotten a smaller one except I once had a smaller one that didn't have enough power to run a laptop I used to own. That is why I got the 300 Watt one. The fan in it is a bit loud though, so I still may pick up a small one that has enough power to run the TV and keep the other one in case I need something with more power.

I was researching battery options for our R-179, and came across this old thread. I wanted to comment that you need to be careful when running an inverter on any 12VDC system, as the watts can add up fast. The reason being that the current draw on the battery is going to be roughly 10X the current on a 120VAC circuit.